Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

019
FXUS63 KLOT 310503
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1103 PM CST Fri Jan 30 2026

.KEY MESSAGES...

- Lake effect snow will continue to result in hazardous travel
  across parts of northwest Indiana tonight.

- Significant snowfall accumulations and dangerous travel expect
  near the lake in northwest Indiana tonight into Saturday.

- Lake effect snow will return to parts of far northeastern IL
  on Saturday. This is likely to result in some additional
  localized accumulations and potential travel impacts on
  Saturday in parts of Cook and eastern Will counties east of
  I-57.

- There may be a period of light snow accumulations Sunday
  night into Monday, followed by less cold conditions by
  midweek.

&&

.UPDATE...
Issued at 957 PM CST Fri Jan 30 2026

Overall the forecast remains on track with only minor
adjustments made to capture current observational trends.

The earlier multi-banded lake effect snow has shifted east into
northwest IN over the past couple of hours. A more dominant
single band is starting to organize just offshore of Porter
County at this hour. A 01z sounding out of Valparaiso University
did showcase steep low-level lapse rates around 6C/km right
through the heart of the DGZ which in combination with lake
induced ELs around 800 mb should support peak snowfall rates
within the band upwards of 2" per hour. While some uncertainty
remains as to how fluid the band will be overnight, there is a
decent signal in guidance for the band to set up over portions
of Porter County for a good part of the night. If this is to
occur then a localized corridor of 6-8 inches of snow may be
seen with higher amounts certainly possible. These snow amounts
in combination with very low visibility will result in dangerous
travel across portions of northwest IN through Saturday morning.
For this reason a Winter Storm Warning remains in effect for
Lake (IN) and Porter Counties through 6 PM Saturday.

Heading into Saturday morning, guidance continues to be very
adamant that the band will begin to shift back west and ooze
into northeast IL between 7-9 AM. As this occurs a building
subsidence inversion should begin to limit the extent of the
instability, but the steep lapse rates coinciding with the DGZ
should still be able to squeeze out some 0.5 to 1 inch per hour
snow rates at times. That said, the inland extent of the lake
effect should be more limited than today since winds are
expected to remain northwesterly through Saturday afternoon. So
expect the higher snowfall amounts (upwards of 3-4 inches) to
likely reside closer to the lake tomorrow. Regardless, some
localized hazardous travel is expected to materialize for
portions of Cook and eastern Will Counties where a Winter
Weather Advisory remains in effect from 6 AM to 4 PM Saturday.

Finally, the lake effect may attempt to wobble back east again
Saturday afternoon but it looks as if the better instability
should be waning by this time. Therefore, expect snow rates to
be on the decrease through Saturday afternoon with the band
fully dissipating during the evening hours.

Outside of the lake effect, another night of single digit
temperatures can be expected before temperatures rebound into
the low to mid-20s Saturday afternoon.

Yack

&&

.DISCUSSION...
Issued at 323 PM CST Fri Jan 30 2026

Headlines...

Headlines are a mess, owing to the expected behavior of the lake
effect band tonight through Saturday. Overall, the band of
impactful snowfall looks to move east into northwestern IN tonight,
then shift back west into parts of northeastern IL on Saturday. As
such, we have multiple headlines in effect for portions of
northeastern IL through Saturday. First, a Winter Storm Warning
remains is in effect for much of Cook through this evening, with a
Winter Weather Advisory covering Lake IL, DuPage (and far
northern Cook) into early this evening. Then, with the
expectation of the snow returning on Saturday, we have opted to
go ahead and issue a second Winter Weather Advisory for all Cook
County zones and eastern Will to cover much of the day
Saturday. Otherwise, we continue the Winter Storm Warning
tonight and on Saturday for Lake (IN) and Porter, only pushing
off the start time a few hours.

Tonight through Saturday...

Lake effect snow showers have been impacting much of northeastern
IL today, with the most intense snow showers as of this writing
falling just inland of the lake from Chicago northward. Expect
this activity to persist through late this afternoon, with
localized snow rates of 1 to 2 inches. As we head into this
evening the broader synoptic flow will back as the mid-level
trough overhead sags to our south. This should foster a transition
in the lake effect character from the ongoing multiple banded
behavior, into a single dominant band of intense snow, with snow
rates possible peaking in excess of 2" per hour. In fact, this
behavior has been noted for several hours today across central
parts of the lake.

It appears this intense band of lake effect snow will quickly
shift southward down the northeastern IL shore after 6 PM this
evening, before settling somewhere across southern Lake Michigan
near, or just east of the Illinois and Indiana state line mid to
late this evening. This thus looks to put parts of Lake County IN
and adjacent areas of western Porter (and perhaps far
southeastern Cook) in the target zone for periods of intense lake
effect snow through the evening. With snow rates of 2"+ per hour,
near white out conditions are likely at times, which will result
in a period of dangerous travel tonight from near the IL and IN
state line eastward along the I-80, I-90 and I-94 corridors right
across Lake and into Porter counties in IN.

This lake effect band is likely to wobble, and/or shift eastward
a bit overnight as a series of meso-lows track southward and crash
onshore across southern Lake Michigan into northwestern IN.
Accordingly, some periodic breaks in the heavier snow are likely
across parts of Lake IN County overnight, (with the snow likely
stopping all together across northeastern IL overnight) as the
main focus (at least temporarily) shifts into Porter County. Lake
induced inversion heights are expected to gradually lower late
tonight into Saturday morning. However, the presence of strong
boundary layer convergence is expected to persist on the lake, and
will thus continue to support some heavier rates of snow within
the main band into Saturday morning.

The forecast consensus continues to favor the focus for this band
of lake effect snow to shift back westward towards the
northeastern IL shore Saturday morning. We thus should see
accumulating snow return to parts of northeastern IL on Saturday,
and it could persist for several hours into Saturday afternoon
before weakening into Saturday evening. While some occasional
heavy rates may persist within the lake effect band on Saturday,
favorable thermodynamics on the lake will continue to fade with
lowering inversion heights through the afternoon. This should thus
result in a lower footprint of the heavier rates of snow as the
band moves into northeast IL on Saturday. Nevertheless, some
localized additional accumulations could exceed 3".

KJB


Saturday Night through Thursday:

Active northwest flow will continue beyond this weekend`s
system and into next week, and will guide several disturbances
across the general region through next week. Medium range
guidance continues to resolve the first of these waves scooting
across the Upper Midwest and Great Lakes region sometime during
the Sunday PM - Monday timeframe. In general, large scale height
falls don`t appear all that impressive, with the main surface
trough and associated low forecast to slide well to our north.
However. fairly robust DCVA on the southern flanks of this
feature, coupled with north-south transient bands of mid-level
f-gen may be sufficient to crank out some light snowfall over
parts of the area, particularly the closer to the Wisconsin
state line you get. The fairly quick forward progression of this
system, as well as a general lack of deeper moisture, suggests
snowfall amounts will be light, probably limited to a few tenths
to an an inch or so. Based on the latest guidance trends, it`s
possible dry air plays a role and ultimately limits snowfall
chances with this feature as well.

Deterministic and ensemble guidance spread increases markedly
after Tuesday, lowering overall forecast confidence during the
middle and end of next week. With a lingering baroclinic zone
just to our south, there`s a potential for some continued
precipitation chances even into Tuesday/Wednesday, but this is
far from ubiquitous across the guidance suite.

While below normal temperatures are expected to continue into
early next week, there` a decent model signal for at least a
moderating trend during the middle and end of the week, with
highs potentially pushing near and above freezing.

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1103 PM CST Fri Jan 30 2026

Forecast concerns for the terminals...

- Band of heavy lake effect snow tonight in northwest IN
  resulting in LIFR visibilities.

- Lake effect to wobble back east Saturday morning resulting in
  a period of IFR to LIFR visibilities at the Chicago terminals.

- VFR conditions outside of lake effect.


The band of lake effect snow continues to organize offshore of
Porter County, IN. While there remains some uncertainty as to
where the band will remain the longest, the general consensus is
for the band to remain mostly over Porter County tonight before
starting to wobble back east around 09-10z. Regardless, under
the band expect LIFR visibilities and snow rates upwards of
2"/hr which could lead to localized accumulations of 6-8 inches
with higher amounts possible.

Heading into Saturday morning, the band is expected to continue
to drift east towards the Chicago terminals. Guidance remains
adamant that the lake effect will ooze back inland by 14-15z
Saturday resulting in another period of IFR to LIFR
visibilities. Though, with the instability expected to be
weakening it seems snow rates will be less (around 1"/hr) and
possibly another 1-4 inches of accumulation. That said, how long
the band parks over the Chicago terminals remains uncertain so
while the the current PROB30s have been maintained through
Saturday afternoon, there is a chance the snow pushes back east
sooner. The snow is finally expected to dissipate late Saturday
evening which will return the terminals to VFR conditions.

Outside of the lake effect, expect VFR conditions to prevail
through the forecast period. However, some MVFR clouds may drift
over northern IL tonight resulting in brief periods of MVFR
ceilings. Winds will also remain northwest around 10 kts through
the period before becoming light westerly winds Saturday night.
Though, periods of northeast winds will occur within the lake
effect snow.

Yack

&&

.HYDROLOGY...
Issued at 230 PM CST Wed Jan 28 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory from 6 AM to 4 PM CST Saturday for
     ILZ103-ILZ104-ILZ105-ILZ108.

IN...Winter Storm Warning until 6 PM CST Saturday for INZ001-INZ002.

LM...Small Craft Advisory until 2 PM CST Saturday for the IL and IN
     nearshore waters.

&&

$$

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